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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'be3c7cf9fc3dde86b4a6cac8abd8cd76a0de4a4bc6454b8249acb27961149c38' 
  AND token = '5/BYyRy3NzyPcuAbqTU9IOQQ/tXz6xVGDLvbZpDXUrE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}